1. Field Of The Invention
This invention is directed to: devices and procedures for emplacing thick viscous materials in a cavity; in one aspect, to such devices and procedures for emplacing a thixotropic material in a microscopic cavity; and in one specific aspect to such devices and methods for emplacing a chemical indicator in a biosensor.
2. Description Of Related Art
Difficulties are encountered in inserting a viscous material into a small cavity or hole. As a wet media is initially introduced into such a cavity, it can effectively seal off an opening into the cavity and trap therein any air in the cavity. Entrapped air can prevent total filling of a cavity and can also become interspersed within the material inserted into the cavity, adversely affecting the material or its performance and degrading certain desired properties (e.g. physical, optical, or chemical) of the material. Other difficulties are encountered when a very small amount (e.g. several nanoliters) of a thick material is to be inserted into a cavity of microscopic dimensions, especially when the amount of the material is critical. Pumping thick viscous material with a conventional syringe or through a conventional pipette has proven to be unsatisfactory.
In one particular technology, the manufacturing of a fiber optic biosensor having a microscopic sized cavity filled with an optical chemical indicator complex, the chemical indicator complex may consist of a solid and liquid matrix of extremely high viscosity, forming a thixotropic paste. In certain embodiments the solid component is a closely packed mass of microscopic particles such as porous ground glass, or plastic microspheres. These solids are the substrate to which the chemical indicator is bonded for immobilization. The liquid component is a viscous polymer water gel or a viscous silicone oil, serving as an ion transport media, a gas transport media for optical coupling media, and an adhesive media for physical integrity. The solids and liquid are mixed in a critical ratio such that the solids are closely packed to the highest possible density, with only enough liquid to fill the interstitial spaces between particles. The chemical indicator cavity in the fiber optic biosensor is a container that holds part of the chemical indicator complex in the optical path of fiber light conductors. The cavity may be as small as 100 microns long, wide, and deep. The cavity is open on one side so that the chemical indicator complex may be installed. The cavity is sealed by covering the opening with a polymer layer. The various difficulties mentioned above have been encountered in attempts to effectively and efficiently insert such a chemical indicator complex into a sensor's cavities.
There has been a need for an effective device and method for emplacing a desired amount of a thick material into a small cavity. There is a need for such devices and methods for introducing a very small amount of a thixotropic material into a microscopic cavity. There is a need for such devices and methods for inserting a known very small amount of a chemical indicator into a microscopic cavity in a fiber optic biosensor.